Journal of Engineering and Thermal Sciences
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Nonlinear models of viscoelastic plates and shells
Full text linkThe dynamics of nonlinear viscoelastic plates and shells is a crucial area of study in modern mechanics, materials science, and engineering. This importance stems from the increasing demand for accurate modeling and analysis of structures subjected to complex loads, as well as the advancement of new materials and technologies. Modern materials, including carbon composites, polymers, and multilayer coatings, possess complex viscoelastic properties. Under dynamic loads, such as vibrations or impacts, viscoelastic materials exhibit time-dependent responses to these loads, necessitating careful consideration of their relaxation and creep characteristics. The unique viscoelastic properties allow these materials to adapt to applied loads, making them highly desirable for the design of sophisticated devices, such as sensors, membranes, and adaptive structures. Furthermore, interactions with external fields – such as electromagnetic or thermal forces – enhance the effects of nonlinearities and require the development of new modeling approaches. The paper presents the equations of dynamics of geometrically and physically nonlinear thin-walled elements. An operator approach based on Rabotnov’s hereditary kernels is proposed, which makes it possible to correctly account for relaxation processes. The novelty of the work lies in the consideration of the combined effect of geometric and physical nonlinearities. To demonstrate the applicability of the model, a numerical example of the deflection of a rectangular plate under uniform loading is examined. Graphs of the deflection evolution and the influence of thickness and relaxation parameters are presented
Innovative design of a gear belt transmission for technological machines
Full text linkThe article presents the types of belt transmission designs, as well as the advantages of their use in mechanical engineering. Belt drives create loads as a result of excessive vibrations due to a flexible element (belt). A new design of an innovative toothed belt drive is proposed, which contains two paired driving and driven gear pulleys with different diameters and two belts with teeth covering them, while the gear ratios of each pair of gears are equal to each other. The simulation demonstrates a 25-38 % reduction in velocity fluctuation compared to conventional drives, confirming the effectiveness of the proposed design
Die casting mold design of CH367B1 aluminum alloy throttle valve body
Full text linkAs a core component of the automotive engine intake system, the throttle valve body is subjected to long-term engine vibrations. Defects such as gas pores and shrinkage pores in the die-cast part will cause uneven stiffness of the throttle valve body, and thus lead to fatigue failure due to local stress concentration under vibration loads. In this paper, the aluminium alloy was used as the die-casting alloy to design an efficient and simple die-casting mould for CH367B1 aluminium alloy throttle valve body. After measuring the target dimensions and conducting a preliminary analysis of the UG 3D drawing of the part, the size and structure of the valve body were analysed according to the 3D model of the part to select the appropriate parting surface. In the design process, the clamping force, chamber capacity, projected area and other parameters were calculated in order to select a suitable die-casting machine. Part-related dimensions and features were analyzed. Push-out mechanisms, molded parts, guide mechanisms, etc. were designed. The whole set of molds was obtained. Suitable casting systems were designed by calculating and checking references. Mold flow analysis was carried out using ProCAST2021 software. The optimal solution was selected by observing the liquid metal filling process and the distribution of defects, and then calibrated
A new self-adaptive anti-galloping device in suppressing conductor galloping in transmission lines
Full text linkConductor galloping is a serious threat to transmission line integrity, inducing excessive conductor tension that may lead to catastrophic failures including conductor breakage and tower collapse. This study proposes a novel self-adaptive anti-galloping device (SAGD) to mitigate galloping amplitudes and reduce associated risks. In this paper a novel self-adaptive anti-galloping device (SAGD) to mitigate galloping amplitudes and reduce associated risks was proposed. The structural design scheme of the device is provided, and its operation sequence was verified through static loading experiments. Conductor free-falling experiments validated the SAGD's vibration control performance, with test results demonstrating its practical applicability for transmission line protection. A finite element model for the conductor-SAGD system was developed, enabling numerical simulation of galloping displacement time history and analysis of endpoint support reaction dynamics. The device's galloping suppression effectiveness is systematically evaluated under varying stroke lengths and threshold conditions
Simulation of motion trajectories and kinematic characteristics of an oscillatory system with a planetary-type vibration exciter
Full text linkThe parameters of the vibration exciters significantly determine the efficiency, reliability, and durability of vibratory technological equipment. This article continues the authors’ previous research dedicated to planetary-type vibration exciters. The main objective at this stage is to substantiate the feasibility of using planetary mechanisms as drives for vibratory machinery. The methodology for conducting virtual experiments involves using the “Motion Analysis” application within the SolidWorks software to simulate the motion of an oscillatory system with a planetary-type vibration exciter. The modeling results are presented as time dependencies of displacements, velocities, and accelerations of the oscillating body (the working element of the vibratory machine), as well as its motion trajectories under different geometric parameters of the planetary mechanism. The scientific novelty of the work lies in the further development of methods for exciting oscillations of the working bodies of vibratory machines with predetermined kinematic and force parameters. The conducted research can be useful for researchers and engineers involved in the investigations and designing of vibratory equipment, aiming to ensure the technologically required motion trajectory and kinematic characteristics of the corresponding working bodies (such as conveying trays, sieves, screens, compacting plates, etc.)
Mechanical response characteristics of railway tunnels under train loading
Full text linkThis study focuses on the mechanical response characteristics of railway tunnels under train loading, which is investigated in depth through model tests. The design of the test covers the similarity ratio, model box, structural model, transducer and loading condition, etc. The model test process includes shaker fixing and model box filling. The test results show that: (1) under different loading frequencies, the acceleration at each measurement point of the tunnel lining cross-section is sinusoidal, which is positively correlated with the frequency, and there is a good third-order polynomial fitting relationship between the loading frequency and the peak acceleration. (2) The peak acceleration of the vault and the left arch foot varies significantly under specific frequency conditions, and the peak acceleration of the superelevation arch grows rapidly; (3) The pattern of change of peak acceleration in the time domain analysis is highly consistent with the pattern of change of amplitude in the corresponding frequency domain analysis. This study provides important data support and theoretical basis for the design, construction and maintenance of railway tunnels, which helps to ensure the safe operation of railway tunnels, and at the same time provides a reference for further in-depth research on the evolution of the performance of the tunnel structure under the action of complex train loads
Torsional dynamics and parametric instability in integrated electric drive systems with PMSM and gear train
Full text linkThis study investigates the vibrational stability and torsional vibration characteristics of an integrated electric drive system composed of a permanent magnet synchronous motor (PMSM) and a two-stage gear pair under parametric excitation. An electromechanically coupled nonlinear torsional dynamic model is established, incorporating electromagnetic effects and time-varying mesh stiffness. The method of multiple scales is employed to analyze the parametric excitation-induced vibrational stability of the system, and the Runge-Kutta method is used to solve the vibrational differential equations and examine the dynamic response characteristics. The results indicate that the system exhibits significant coupled vibrational behavior: the spectrum of the dynamic meshing force contains not only the meshing frequency of the current gear pair but also the system’s natural frequencies and meshing frequency components from other gear stages. Under conditions without external excitation, the system is found to exhibit not only primary resonance responses due to time-varying mesh stiffness excitation but also various nonlinear vibrational phenomena such as subharmonic resonance, superharmonic resonance, and combination resonance. The response is particularly pronounced near twice the first-order natural frequency
A k-kNN miscalibrated current transformer identification method based on line topology for distribution networks
Full text linkThe operational duration and environmental factors associated with current transformers (CTs) in distribution networks makes them prone to measurement miscalibration during their operation. To address this, a kernel k-nearest neighbor (k-kNN) miscalibrated CT identification method based on line topology is proposed. This method relies on the composite characteristics of load currents specific to certain line topologies. High-precision secondary-side CT current data provided by the current acquisition devices in the feeder area are used to construct a multiple linear regression model. The multiple linear regression model is established in the complex domain, and indirectly assesses the measurement status of the current transformers by analyzing the complex coefficients. Building upon the kNN identification algorithm, a kernel function is introduced to map low-dimensional distance feature vectors into a higher-dimensional feature space where linear separability is significantly enhanced, thus improving the accuracy with which abnormal coefficients can be detected in the multiple linear regression model. Experimental simulations and field application scenarios demonstrate that the proposed method significantly outperforms traditional kNN algorithms in terms of classification performance. Specifically, there is an increase of 12.0 % in the F1 score, a rise of 13.3 % in accuracy, and an improvement of 12.0 % in recall. Moreover, in practical engineering applications, the recognition metrics consistently exceed 93 %, which substantiates the effectiveness of the proposed miscalibrated CT identification method
Design peculiarities and kinematic analysis of a shaking conveyor with multiple transporting and screening trays
Full text linkThe paper focuses on the design peculiarities and kinematic analysis of a novel shaking conveyor equipped with three interconnected transporting and screening trays. The goal is to develop a comprehensive mathematical model to describe the system’s motion and analyze the interplay between the trays, providing a basis for improved design and optimization. The scientific novelty lies in the detailed kinematic study of this specific multi-tray configuration, particularly the interaction of the dual beam systems actuating the intermediate tray, leading to complex coupled motion profiles. The practical value of the research is substantial for designing and optimizing such multi-functional vibratory equipment, as the kinematic data (displacements, velocities, accelerations) provide critical insights into material-tray interaction, aiding in predicting and enhancing material processing efficiency, estimating inertial loads for robust structural design, and informing vibration isolation strategies. The methods employed include the development of a kinematic diagram and corresponding motion equations for the multi-loop linkage mechanism, followed by numerical modeling of the system’s motion using Wolfram Mathematica software. The main results characterize the complex motion profiles for a steady-state operational frequency of 10 Hz, revealing distinct amplitudes and near-linear inclined trajectories for key hinges representing each tray. Notably, the upper tray exhibited the most significant displacements and accelerations, with horizontal accelerations reaching approximately 3 g and vertical accelerations around 1.3 g, indicating a motion profile conducive to effective material lifting, “throwing”, and bed stratification. Scopes of further research include a complete dynamic analysis incorporating mass properties and driving forces, experimental validation of the models, optimization of geometric and operational parameters, integration with Discrete Element Method (DEM) simulations for detailed material flow analysis, and investigations into wear, fatigue life, and advanced control strategies
Determination of optimal drive parameters for high-speed linear systems
Full text linkThe problem of optimizing the drive design parameters for a high-speed linear system is solved based on minimizing the inertial torque. New analytical expressions are obtained for determining the optimal gear ratio of the intermediate transmission, taking into account the moments of inertia of rotating masses, the carriage mass, and the screw pitch. An optimization problem is proposed to determine the number of gear teeth and the screw pitch by minimizing a function that includes the relative error between the actual and calculated gear ratio, as well as the total number of teeth required to ensure the specified travel speed of a carriage. At the next calculation stage, the number of gear teeth is refined based on the nearest standard screw pitch values. The resulting parameters are evaluated using a transient dynamic analysis according to key kinematic and energy characteristics